A newly developed angiotensin II type 1 receptor antagonist, CS866, promotes regression of cardiac hypertrophy by reducing integrin β1 expression

Abstract

Previous studies have demonstrated that integrins link the extracellular matrix to the hypertrophic response pathway of cardiac myocytes in vitro. To examine the direct relation between integrin β1 and cardiac hypertrophy in vivo, we studied the effects of a newly developed angiotensin II type 1 (AT1) blocker, CS866 (ARB; 10 mg/kg/day), an angiotensin-converting enzyme inhibitor, temocapril (ACEI, 10 mg/kg/day), or both on modulation of integrin β1 in the hypertrophied hearts of stroke-prone spontaneously hypertensive rats (SHRSP) 6 to 12 weeks of age. Treatments with ARB, ACEI, and combination therapy significantly reduced systolic blood pressure. However, the reduction in cardiac hypertrophy was greater in SHRSP treated with ARB or combination therapy than in those treated with ACEI. Multiplex reverse transcription-polymerase chain reaction revealed significantly higher mRNA expression of atrial natriuretic factor, AT1 receptor, and integrin β1 in untreated SHRSP than in normotensive Wistar-Kyoto rats (WKY). The mRNA levels of ANP, AT1 receptor, and integrin β1 in SHRSP were significantly decreased by treatment with ARB, ACEI, or combination therapy. Decreased mRNA expression of ANP, AT1 receptor, and integrin β1 in the treated SHRSP was associated with reductions in blood pressure; ARB and combination therapy produced greater decreases in expression than did ACEI. These observations suggest that CS866 has a beneficial effect on myocyte hypertrophy and that down-regulation of AT1 receptor and suppression of integrin β1 participate in the regression of pressure-induced cardiac hypertrophy in vivo. The correlation between the expression of integrin β1 and AT1 receptor was significant. Our results also suggest that integrin expression by myocytes might be modulated by angiotensin II via AT1 receptor.